High-pressure pipe string for continuous fusion drilling of deep wells, process and device for assembling, propelling and dismantling it

ABSTRACT

A high pressure pipe string for continuous fusion drilling of deep wells which houses supply lines, measurement instrumentation and control wiring of the drilling device. It has at least two shell elements forming two halves of a pipe, and these parts are assembled into a smooth, tight, and compression and tension resistant pipe. In a process for assembling, propelling and subsequently dismantling a high-pressure pipe string for continuous fusion drilling of deep wells, the supply lines, the measurement instrumentation and the control wiring are fed to the boring head in a continuous manner. The supply lines, the measurement instrumentation and the control wiring are encased in a tight, compression and tension resistant high-pressure pipe string having several parts, the assembled pipe string being continuously propelled downward into the boring. The device for the execution of one of these processes has one storage carrousel for each of the supply lines, on which the supply lines are wound. Such a storage carrousel has a circular, rotating and motor-driven platform designed to hold the wound up supply lines. It also has a multi-level assembly tower housing the elements for assembling the pipe segments, to propel the pipe string downward into the boring, and to subsequently retrieve and dismantle the pipe string.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a high-pressure pipe string for the continuousfusion drilling of deep wells. It relates further to a process for theassembly of this high-pressure pipe string, for propelling it in theboring and for dismantling it. This invention also relates to anapparatus for the execution of the afore-mentionned processes.

Continuous fusion drilling is a drilling method in which extremely hightemperatures are generated at or slightly ahead of the boring head,leading to the melting of the rock. The rock melt is evacuated into thesurrounding, thermofractured (fractured by local thermal stresses) rockformation by high, locally applied pressure. The boring head can, as aresult, be continuously propelled forward, melting the rock ahead of itand pushing the melt out into the surrounding cracks.

2. Description of Prior Art

Two continuous fusion drilling techniques are described in the Germanpatent specification DE25 54 101 C2 and in the German patent disclosure37 01 676 A1. The temperatures required to melt the rock are generatedby high-pressure, hydrogen/oxygen flame jets. The process according tothe German patent specification DE25 54 101 C2 is designed to effectuatea total evacuation, by high applied pressure, of the rock melt into thesurrounding rock. The process according to the German patent disclosure37 01 676 A1, on the other hand, is a profiling fusion drilling processin which only a minimal, outer profile of the boring is melted andremoved, to provide a passage for the drilling device and the supplylines. The resulting melt from this area is pushed into the drillingcore. After a partial cooling, the core segments are sheared off andremoved to the surface. Both fusion drilling processes are designed tooperate in a continuous fashion, i.e. the deep well is completed in asingle, continuous thrust. The cooled melt forms a casing for the borehole, thus providing a guide channel for the fusion drilling device andpreventing cave-ins of the boring walls. The bore head can be designedfor a specified service life, so that deep wells up 10,000-15,000 meterscan be realized in a single, continuous process, without any time andenergy-consuming "round trips."

Reliable processes must be chosen to prevent technical problems leadingto interruptions of the fusion drilling process. This means processesthat incorporate a minimal number of possible sources of problems, andwith a sufficient redundancy in the operational systems so that areplacement unit can immediately take up the functions of any defectivepart of the system. A continuous drilling process significantly raisesthe boring velocity and can thus drastically reduce the costs ofrealizing a deep well. These advantages are intrinsic qualities of thefusion drilling process, which eliminates the need for the "round trips"to change the bore head and the boring rods or pipes or to remove thecore, which characterizes conventional, mechanical boring methods. Theseadvantages can, however, only be exploited if the power supply to andcontrol of the bore head can also be performed in a continuous manner. Acontinuous supply of hydrogen, oxygen and cooling water at a pressure ofabout 2,000 bars and a vertical, mechanical driving force to the borehead are required for the realization of continuously fusion-drilleddeep wells. The risk of leaks or ruptures in the joints and thepossibility of signal interruptions in control wiring connectorspractically exclude a segmental assembly of the high-pressure hydrogen,oxygen and cooling water supply lines. Other means must therefore beprovided to carry out the continuous power supply and uninterruptedcontrol of the bore head. These means must allow the forward motion andretrieval of the pipe string with all its supply lines and its controlequipment.

SUMMARY OF THE INVENTION

An object for this invention is to provide a high-pressure pipe stringfor the continuous fusion drilling of deep wells. A further object forthis invention is to provide a process for the assembly of thishigh-pressure pipe string, for propelling it in the boring and fordismantling it after completion of the well.

The proposed object is achieved, according to one preferred embodimentof this invention, by a high-pressure pipe string which houses thesupply lines, the measurement instrumentation and the control wiring forthe drilling device. Its construction, has at least two shell elementsforming the two halves of the pipe segments and can be assembled into acontinuous, smooth, tight, and compression and tension resistant, pipe.

The proposed object is also achieved by a process for the assembly, thepropelling and the subsequent dismantling of a high-pressure pipe stringfor the continuous fusion drilling of deep wells. In the process, whosespeed is synchronized to the boring velocity, the continuous supplylines, the measurement instrumentation and the control wiring areencased in a modular, segmentally assembled, high-pressure pipe stringand continuously fed to the drilling device.

The proposed object is further achieved by a device for the execution ofthe above-mentioned process. The device has a storage carrousel and anassembly tower. The storage carrousel receiving the wound up supplylines, the measurement instrumentation and the control wiring consistsof a circular, rotating, motor-driven platform. The multi-level assemblytower houses the means to assemble the pipe segments, to propel the pipestring downward into the boring and to dismantle the pipe string aftercompletion of the deep well.

BRIEF DESCRIPTION OF THE DRAWINGS

The description of the invention is supported by the followingillustration wherein:

FIG. 1 exploded view of the three main components of a high-pressurepipe string segment.

FIG. 2 top view of the assembled high-pressure pipe string.

FIG. 3 typical connection between two pipe string segments.

FIG. 4 shows a sectional view of an assembly tower for the assembly,propulsion, and dismantling of the high-pressure pipe string.

FIG. 5 perspective view with a cut-out of a supply carrousel.

DESCRIPTION OF PREFERRED EMBODIMENTS

The principal features of the high-pressure pipe string according to theinvention as well as especially advantageous processes and devices forthe execution of the processes are described in the patent claims andexplained more in detail in the following description.

The hydrogen, oxygen and cooling water supply lines to the boring headas well as the control and measurement wiring according to the inventionare continuous. This means the supply and control lines must be producedin one continuous, up to 15 km long, piece for the total length of theboring. These pipes must therefore be produced on site, since the totaldimensions of the system make transportation prohibitive. The hydrogenand oxygen supply lines are made of an appropriate steel alloy. Thesesupply lines must be able to withstand a pressure of about 2000 bars andmust have an outside diameter of about 20 mm. The cooling water linesare somewhat larger, with an outside diameter of about 50 mm. The wallthickness of the supply lines should be about 1/4 to 1/3 of the outsidediameter in order to withstand the high pressures. Such profiles canrelatively easily be wound into loops with a radius of about 20 mwithout undergoing any plastic deformation. Even pipes with larger radiiwould remain elastic at this large winding radius.

The invention concerns a high-pressure pipe string which would feedthese supply lines into the boring in a continuous manner. Thehigh-pressure pipe string is designed to contain and protect the systemof supply lines. It furthermore should take up the tensile andcompressive forces necessary to propel the bore head forward and toretrieve it after the deep well is completed.

FIG. 1 shows a pipe string segment before assembly. It comprises ofthree parts: an inner profile 1 with a central pipe 2 having fourprofiles 3 arranged in a cross shape on its outer side, and two similarshell elements 4, forming the two halves of a pipe segment. These shellelements have radial ribs 5, 6, 7 on their inner side. The geometry ofthe three parts 1, 4 is such that the ribs 5, 6, 7 on the inner side ofthe shell elements fit on the outer edge of the inner profiles 3. Thehatched areas on the parts 1, 4, as shown in FIG. 1, are designed to befitted together and bonded. The inner profile 1 is mounted on the fusiondrilling device or on the tail section of the high-pressure pipe stringbefore assembly of the two outer segments 4. The continuous supply lines10, 11 are fastened within the open areas 8 of the inner profile 1 bymeans of isolating mounts 9. The mounts 9 hold the lines 10, 11 in placeby frictional forces. The outer shell segments 4 are then assembledaround the inner profile 1 carrying the supply lines 10, 11. Theassembly is accomplished with a heat resistant, hot-curing,industrial-grade adhesive with a high shear and tensile strength. Thepipe string is extended by the assembly of successive sets of thesethree parts.

FIG. 2 shows a top view of an assembled pipe segment. The cross section,with a hollow profile having four open areas 12-15, combines a highstability and low weight. All continuous supply lines for hydrogen 10,oxygen 11 and cooling water 16 as well as the wiring for the measurement17 and control 18 systems of the bore head are fastened to the innerprofile with isolating mounts 9.

FIG. 3 shows a connection between two successive pipe segments 30, 31.Each segment has a length of about 20 m. The outer shell elements have alip 32, 33 at each end. A two-part stabilizer ring 34, 35 is mountedbehind each of the flanges formed by these lips 32, 33. The two halvesof these rings are adhesively bonded together and to the pipe. They canadditionally be screwed together, for an increased bond strength. Thestabilizer rings 34, 35 reinforce the pipe and provide an increased areafor bonding at the ends of the pipe segments 30, 31. Two-part fasteningsleeves 36, 37 are mounted over the stabilizing rings 34, 35 and bondedto them. These sleeves 36, 37 can be screwed together in the axialdirection, thus pulling together the adjoining pipe segments 30, 31 andsecuring them during bonding. This connection allows a large number ofpipe segments to be joined to form a long high-pressure pipe string. Theconnection is strong enough to take up the tensile loads imposed on thepipe string during its retrieval after the completion of a deep well.The pipe string can be pulled up by a hydraulic jack system whosecatches or grippers would grasp the fastening sleeves 36, 37 of theconnection. A further function of the connections is to act asdistancers between the pipe string and the walls of the boring, toprotect the pipe from frictional damage. The dismantling of the pipestring 48 after completion of the boring is carried out in reverseassembly order. The adhesively bonded surfaces are separated by heatingthem to a temperature above the heat resistance temperature of theadhesive. The individual components can thus be recovered.

The components of the pipe are assembled into a tight, tension andcompression resistant, high-pressure pipe string in a multi-levelassembly tower located over the boring site. The tower also provides themeans to lead the continuous supply lines and the measurement andcontrol wiring into the boring and to apply pressure on the fusiondrilling device. Such an assembly tower 40 is shown in FIG. 4. It isdivided into four levels 41-44. The continuous supply lines 10, 11, 16for hydrogen oxygen and cooling water are supplied by a carrousel,described below. They are led through a deflector 55 to the top of thetower 40, where a pulley 45 guides them vertically back down into thetower 40. The circumference of the pulley is equipped with rubbergrooves to hold and pull the individual supply lines 10, 11, 16. Themeasurement and control wiring are not shown here. They can compriseelectrical or glass fiber cables which can be supplied off a muchsmaller spool located on or in the assembly tower.

The assembly process of the pipe string 48 is carried out in acontinuous manner within the tower 40 by automated, computer-controlledrobots 50, 51. The inner profile 1 of the pipe string 48 is assembled inthe upper level 44. The inner profiles 1 could be stored in the upperlevel 44 and supplied to the assembly robots 50 by a conveyor. Theassembly robots 50 seize the profile 1, for example by means ofelectromagnetic "hands" 38, and set it on the previously mounted pipesegment. In the following step, they install the isolating mounts 9, bymeans of which they then attach the supply lines 10, 11, 16 and themeasurement and control wiring to the inner profile 1. Once all supplylines and cables are in place, the assembly robots 50 install and bondthe external shell elements 44. These shell elements can also be storedin the assembly tower 40 and brought to the work area by a conveyor. Theheat curing of the adhesive takes place during the conveyance of theassembled pipe segment from the fourth to the third level. It can becarried out by heating elements incorporated in the joints of the pipeof by external thermal elements. For example, a heated hydraulic moldingpress (not shown) could be used to hold the parts together and to curethe adhesive in a continuous manner during the boring process. On thethird level 43, another line of assembly robots 51 installs thestabilizer rings 34, 35 behind the flanges of the ends of the individualpipe segments, as described earlier. This is followed by the mounting ofthe fastening sleeves 36, 37. Here again, the supply of parts and theirinstallation is performed in an automated way by a computer-controlledsystem of conveyors and assembly robots 51 equipped with electromagnetic"hands" 39. These bring the parts into position, press them onto thepipe segment, and heat them for the amount of time required for theadhesive to cure. This process is carried out along with the advance ofthe pipe string 48 corresponding to the boring speed.

The hydraulic lifting system, consisting of two sets of hydraulic jacks53, is located in the first and second levels 41, 42. The jacks 53convey the high propelling pressures necessary for the fusion drillingprocess over the pipe string 48 to the boring head. They are alsodesigned to lift the relatively heavy full length of pipe string 48 outof the boring after completion of the well. Each of the two hydrauliclifting systems 46, 47 is equipped with hydraulically powered 52grippers 49. These grippers 49 grasp the pipe string 48 right over aconnector sleeve 36, 37 when pushing the pipe string downward, and underthe sleeve when lifting the pipe string. The force for the upward anddownward translation of the pipe string is provided by two sets ofhydraulic jacks 53. The system is slightly over-designed in order toensure an uninterrupted boring operation in the event that one of thejacks 53 should fail. The force is transmitted from the jacks 53 to thegrippers 49 over a continuous beam. The use of two such lifting systems46, 47 arranged on two levels allows an alternating operation of the twolifting systems 46, 47. This is shown in FIG. 4, where the one set ofjacks 53 is pushing the pipe string downward while the other set ofjacks 53 is moving upward, with grippers 49 open, in order to recover astandby position for the next forward stroke cycle of the pipe string48.

Pipe strings with larger diameters can further be strengthened by avacuum stabilization system. This consists of sealing each new assembledpipe string segment and creating a vacuum in it. The pipe segments canbe equipped with valves through which the inner spaces of the pipe areevacuated.

The cooling water is pumped to the boring head under high pressure inorder to keep it in a liquid phase. This optimizes the heat exchange andthus the cooling capacity of the water. At the end of its cooling cycle,the water is evacuated from the boring head at its upper side, into thespace between the sides of the pipe and the walls of the boring. Thepressure of the injected cooling water must be significantly higher thanthat of the water which is already in the boring. Thus, the releasedenergy of the cooling water can further be used for driving the boringhead forward. Steam powered lateral course-correction actuators arelocated right over the fusion drilling device, in the space between thesides of the pipe string and the walls of the boring. These actuators,which ensure that the boring head stays along its vertical path, arecontrolled by a signal generated by a gravitation sensor and transmittedby laser over a fiber optic cable. The steam pressure is provided bysteam generators located in the fusion drilling device.

Should the pipe string 48 reach a mass exceeding the lifting capacity ofthe hydraulic systems, 46, 47 or of the connections between theindividual segments, an additional step must be added to the retrievalprocedure. Once the boring is completed, the pipe string 48 is severedright above the fusion drilling device in such a way as to seal its end,and the space between the sides of the pipe and the walls of the boringis fully flooded. Since the pipe string is hollow, its weight is reducedby the difference between its mass and that of the displaced water. Theresulting buoyancy contributes to the lifting force necessary toretrieve the pipe string.

FIG. 5 shows a storage carrousel 60 holding the continuous supply lines10. The integral length of supply lines needed for a given deep well isstored on and continuously unwound from the carrousel 60. Thiseliminates the need for joints which could form weak links in the lines.The necessary pressure, cooling and power units as well as the storagetanks 61 are incorporated in the carrousel 60. Such a carrousel 60comprises a round, rigid platform 62 set on a circular set of rails 63.The rotation of the platform can be driven by a gear drive powered byone or several synchronized electrical motors. The various power andcontrol units and the storage tanks 61 are located at an inner side ofthe platform 62, at the center of the carrousel 60. An access road 64for tank trucks 65 surrounds the supply carrousel 60. The tanks 61 canbe refueled during the operation of the carrousel 60. The inner end ofthe supply lines is connected to the tanks over a pumping unit, so thatthe lines 10 can continuously be supplied with liquid hydrogen, oxygenand cooling water. The supply lines 10 are stored, as on a shelf, inseveral hundred layers and windings on the outer area of the platform62. The outer edge of the individual layers is held by hydraulicallyadjusted rings 66 forming a wall around the circumference of thecarrousel 60. The rings 66, designed to hold in place and protect thesupply lines, are moved downward by hydraulic jacks 67 placed around thecarrousel 60, and expose only the top layer of stored supply lines 10 inorder to ensure a smooth unwinding of the continuous lines. The storedsupply lines 10 are covered by a watertight, insulating tarp 69. Thesupply lines 10 are unwound at a speed corresponding to the boringadvance and carried by a hydraulically controlled conveyor 68, in alarge arc, to the assembly tower. The supply lines 10 must always bekept above their calculated minimal bending radii in order to preventdamage through plastic deformations of the pipe walls. A separatecarrousel 10 is available for each type of supply line, in order toavoid synchronization problems if pipes of different diameters are used.The rotation speed of the various carrousels 60 is coordinated by anappropriate adjustment of the drive motor speeds. An equal conveyancevelocity of all supply lines 10 to the assembly tower 40 is thus alwaysguaranteed.

I claim:
 1. A process for assembling and propelling a high-pressure pipestring for continuous fusion drilling of deep wells which comprises:feeding supply lines (10, 11, 16), measurement instrumentation wiring(17) and control wiring (18) to a boring head in a continuous manner;encasing the supply lines (10, 11, 16), the measurement instrumentationwiring (17) and the control wiring (18) in a tight compression andtension resistant high-pressure pipe string comprising a plurality ofpipe segments each comprising an inner profile (1) having a central pipe(2) with a plurality of profiles (3), and a plurality of shell elements(4) secured about the inner profile (1); and propelling the assembledpipe string continuously downward into a boring.
 2. A process accordingto claim 1, wherein the supply lines (10, 11, 16), the measurementinstrumentation wiring (17) and the control wiring (18) are fed to theboring from a storage carrousel (60) on which a full required length ofthe supply lines (10, 11, 16) for the boring is stored.
 3. A processaccording to claim 2, wherein the high-pressure pipe string is assembledwith an industrialgrade, hot-curing adhesive.
 4. A process according toclaim 3, wherein an inside of the pipe string is sealed and evacuated toraise stability of the pipe string.
 5. A process according to claim 4,wherein the high-pressure pipe string encasing the supply lines (10, 11,16), the measurement instrumentation wiring (17) and the control wiring(18) is carried out by computer-controlled assembly robots (50, 51). 6.A process according to claim 5, wherein the high-pressure pipe string isguided by a plurality of steam powered lateral course-correctionactuators positioned directly over a fusion drilling device, betweensides of the pipe string and walls defining the boring, and iscontrolled by a gravitation sensor-emitted signal.
 7. A processaccording to claim 6, wherein retrieval of the high-pressure pipe stringfor its dismantling, once boring is completed, is accomplished bysevering the pipe string directly above the fusion drilling device insuch a way as to seal an end of the pipe string, and flooding a spacebetween the sides of the pipe and the walls of the boring, therebyreducing a weight of the pipe string by a difference between a mass ofthe pipe string and that of the displaced water, and a resultingbuoyancy contributes to a lifting force necessary to retrieve the pipestring.
 8. A system for assembling and propelling a high-pressure pipestring for continuous fusion drilling of deep wells, the systemcomprising: at least one storage carrousel (60), an assembly tower (40),the storage carrousel (60) receiving a plurality of wound up supplylines (10, 11, 16), measurement instrumentation wiring (17) and controlwiring (18), the storage carrousel comprising a circular, rotating andmotor-driven platform (62), and a multi-level (41 to 44) assembly tower(40) housing means (50, 51; 46, 47) for assembling a plurality of pipesegments and for propelling the pipe string downward into a boring.
 9. Asystem according to claim 8, wherein the assembly tower (40) houses ahydraulic jack system (46, 47) for continuous, two-cycle propelling ofthe pipe string.
 10. A high-pressure pipe string for continuous fusiondrilling of deep wells comprising: the pipe string housing a pluralityof supply lines (10, 11, 16), measurement instrumentation wiring (17)and control wiring (18) for a bore head; the pipe string comprising atleast two shell elements (4) forming the two halves of a plurality ofpipe segments of the pipe string; and means (3, 5 to 7) for assemblingthe pipe segments into a continuous, smooth, tight, and compression andtension resistant, pipe.
 11. A high-pressure pipe string according toclaim 10, wherein stability of the pipe string is increased with atleast one inner profile element (1) positioned inside of the pipe stringand secured to the shell elements (4) of one of the pipe segments.
 12. Ahigh-pressure pipe string according to claim 11, wherein the assemblingmeans comprise a plurality of smooth, plane bonding surfaces (5 to 7)which can be bonded by a hot-curing, industrial-grade adhesive with ahigh shear and tensile strength.
 13. A high-pressure pipe stringaccording to claim 12, wherein isolating mounts 9 holding in place, byfrictional forces, the continuous supply lines (10, 11, 16, 17, 18) aremounted in open areas (12 to 15) between profiles of the inner profileelement (1) and the pipe string.
 14. A high-pressure pipe stringaccording to claim 13, wherein the inner profile element (1) and theshell elements (4) in two adjacent said pipe segments are at least oneof adhesively bonded and screwed together with a stabilizing ring (34,35) and a fastening sleeve (36, 37).
 15. A process according to claim 1,wherein the high-pressure pipe string is assembled with anindustrial-grade, hot-curing adhesive.
 16. A process according to claim1, wherein an inside of the pipe string is sealed and evacuated to raisestability of the pipe string.
 17. A process according to claim 1,wherein the high-pressure pipe string encasing the supply lines (10, 11,16), the measurement instrumentation wiring (17) and the control wiring(18) is carried out by computer-controlled assembly robots (50, 51). 18.A process according to claim 1, wherein the high-pressure pipe string isguided by a plurality of steam powered lateral course-correctionactuators positioned directly over a fusion drilling device, betweensides of the pipe string and walls defining the boring, and iscontrolled by a gravitation sensor-emitted signal.
 19. A processaccording to claim 1, wherein retrieval of the high-pressure pipe stringfor its dismantling, once boring is completed, is accomplished bysevering the pipe string directly above a fusion drilling device in sucha way as to seal an end of the pipe string, and flooding a space betweensides of the pipe and walls of the boring, thereby reducing a weight ofthe pipe string by a difference between a mass of the pipe string andthat of the displaced water, and a resulting buoyancy contributes to alifting force necessary to retrieve the pipe string.
 20. A high-pressurepipe string according to claim 10, wherein the assembling means comprisea plurality of smooth, plane bonding surfaces (5 to 7) which can bebonded by a hot-curing, industrial-grade adhesive with a high shear andtensile strength.
 21. A high-pressure pipe string according to claim 10,wherein isolating mounts 9 holding in place, by frictional forces, thecontinuous supply lines (10, 11, 16, 17, 18) are mounted in open areas(12 to 15) between profiles of the inner profile element (1) and thepipe string.
 22. A high-pressure pipe string according to claim 10,wherein the inner profile element (1) and the shell elements (4) in twoadjacent said pipe segments are at least one of adhesively bonded andscrewed together with a stabilizing ring (34, 35) and a fastening sleeve(36, 37).